I don't know that fly sparging will necesarily increase your efficiency. I generally get ~75% batch sparging and I don't even usually 'sparge' perse. I mash pretty thin ~2 qt/lb and step the temp up to mash out range before running off and still git 73%

I would look in other areas (Specifically mash pH) before assuming it's the batch sparge

Just found fly sparging is single infusion, full body. Didn't discover that until I chose single infusion and look at the mash tab. Under the mash step list it says to fly sparge with the gallons and temp for the brew. brew Smith is great software but has many bugs that don't seem to get fixed.

I brew big beers typically with 17 to 23 pounds grain. Read on another web site a brewers efficiency starts to drop around 17 pounds grain, otherwise he gets 75% fly sparging. Has anyone else experienced lower inefficiencies with large grain bills?

Currently mash for 60 min and batch sparge for 30. Will try mashing for 60, fly sparge for 30 and check pH. What effect does pH have on efficiency? How do you control for it? What should a good pH be?

If fly sparging does not increase efficiency will mash for 90 and batch sparge for 45.

I batch sparge and average 83-85% efficiency. If you want to increase your efficiency, the crush is the first place to look.

+1 on this. I was getting low OG's on a couple batches. Checked my "gap" and it slid open a bit. I guess I didn't tighten those thumbscrews enough. I re-adjusted to 0.025 and all is good. I'm hitting beersmith numbers at 80% right on. I was fearful of getting a stuck sparge at that narrow of a gap, but everything seems to be working great. Some husks are broken, but vast majority are still whole. And the first batch of our Flagship Agnew Amber turned out just as we expect it to.

Currently mash for 60 min and batch sparge for 30. Will try mashing for 60, fly sparge for 30 and check pH. What effect does pH have on efficiency? How do you control for it? What should a good pH be?

If fly sparging does not increase efficiency will mash for 90 and batch sparge for 45.

Why are you batch sparging for so long> There's nothing to be gained from it. Again, look t your crush...that's the first place to increase your efficiency. Mashing for longer will increase the fermentability of the wort, but it will not increase your efficiency unless you're not getting full conversion for some reason at 60 min. Have you checked that?